A conventional communication device is described as follows with reference to FIG. 7.
FIG. 7 is a view of upper and lower surfaces of a conventional communication device. In FIG. 7, communication device 1 includes board 2 and semiconductor circuit 3 for generating signals. Semiconductor circuit 3 is disposed on the lower surface of board 2 and connected to board 2 through via 4, which is placed on the upper surface of board 2 and formed in board 2. Communication device 1 further includes amplifier 5 and antenna terminal 6. Amplifier 5 is connected to the output of semiconductor circuit 3. Antenna terminal 6 is connected to amplifier 5.
Communication device 1 further includes ground planes 7 and 8. Ground plane 7 is disposed on the lower surface of board 2 and connected to amplifier 5. Ground plane 8 is disposed inside board 2 and connected to semiconductor circuit 3. Ground planes 7 and 8 are connected to each other through ground via 9, and further connected to amplifier 5 through thermal vias 10 for radiating amplifier 5.
An example of a conventional technique related to the present invention is shown in Patent Document 1.
In conventional communication device 1, the region in which amplifier 5 is located and the region in which semiconductor circuit 3 is located partially overlap with each other. This makes a large number of signal lines of semiconductor circuit 3 hinder providing a sufficient number of thermal vias 10 to be connected to amplifier 5. As a result, floating inductance tends to occur between amplifier 5 and ground planes 7, 8, thereby being more likely to cause abnormal oscillation of amplifier 5.
Patent Document 1: Japanese Patent Unexamined Publication No. 2006-121147